The present invention relates generally to petrified cellulosic materials, and more particularly to petrified cellulosic materials that are added to wellbore treatment fluids.
In the exploration for oil and gas, wellbore treatment fluids (e.g., drilling fluids and cement slurries) are used. In well drilling, a drilling fluid servicing fluid, or mud is pumped down through the drill stem of the rotary rig, circulated around the drill bit and returned to the surface through the annular passage between the drill stem and the well wall. The drilling fluid lubricates the drill stem and bit, cools the bit and carries the cuttings from the bit up to the surface. The drilling fluid also provides a hydrostatic head against the walls of the well to contain downhole geo-pressure.
One of the main functions of cement compositions is to maintain the well integrity during the well's lifetime, which can be more than 30 years. The cement reduces the risk of uncontrolled flow of oil or gas (e.g., provides permeable-zones isolation), provides mechanical support for the casing string, protects casing from corrosion, and supports the wellbore walls to prevent collapse of formations. Cements are further used to make permanent or temporary seals (plugs).
Typical wellbore treatment fluids (e.g., drilling fluids, completion fluids, fracturing fluids, and cements) contain a number of additives, each satisfying a specific purpose. For example, additives are used to control the rheology of the wellbore treatment fluid, to improve its filtration properties and/or increase its density. Notwithstanding the cost associated with such additives, the overall cost of the drilling operation is decreased by the improvement made by these additives on the drilling rate and hole-cleaning processes.
Typical additives include proppants, weighting agents, fluid loss control agents, and gravel pack materials. These additives are generally round or spherical in shape, and are formed from materials such as glass or ceramics. Other morphologies or shapes, however, may be more suited for the different purposes of the additives. To manufacture additives in these desired shapes requires high energy and high temperatures, which results in a very expensive process.
Thus, there is a continuing need for improved methods and compositions for additives in wellbore treatment fluids.